1. Field of the Invention
The present invention relates generally to computer data communication networks, and more particularly, to a multiprocessor computer architecture having plural switching modules for transferring data packets between computer networks and a control module for performing load balancing to ensure efficient utilization of the computer networks in which a software interface is defined between the switching module and the operating system for transferring data packets therebetween.
2. Description of Related Art
Computer networks are widely used as a way to communicate messages between computers. The Internet is made up of more than 100,000 interconnected computer networks spread across over 100 countries, including commercial, academic and government networks. Originally developed for the military, the Internet has become widely used for academic and commercial research. Today, the Internet has become commercialized into a worldwide information highway, providing information on every subject known to humankind. Similarly, businesses and other entities have adopted the Internet paradigm as a model for their internal networks, or so-called xe2x80x9cintranets.xe2x80x9d
Messages transferred between computers within a network are typically broken up into plural data packets. Packet switching systems are used to route the data packets to their required destination and enable the efficient handling of messages of different lengths and priorities. Since each data packet includes a destination address, all packets making up a single message do not have to travel the same path. Instead, the data packets can be dynamically routed over the interconnected networks as circuits become available or unavailable. The destination computer receives the data packets and reassembles them back into their proper sequence to reconstruct the transmitted message.
Internet computer networks generally use the TCP/IP communications protocol, which is an acronym for Transmission Control Protocol/Internet Protocol. The TCP portion of the protocol provides the transport function by breaking a message into smaller packets, reassembling the packets at the other end of the communication network, and re-sending any packets that get lost along the way. The IP portion of the protocol provides the routing function by giving the data packets an address for the destination network and client at the destination network. Each data packet communicated using the TCP/IP protocol includes a header portion that contains the TCP and IP information. Another communication protocol used in communication between Internet computer networks is UDP/IP, in which UDP is an acronym for User Datagram Protocol. UDP is used in place of TCP in conditions when a reliable delivery is not required. For example, UDP/IP is often used for real-time audio and video traffic where lost data packets are simply ignored, because there is no time to retransmit. Since the computer networks connected to the Internet may use other communication protocols besides TCP/IP or UDP/IP, gateways are used to convert data packets from these protocols into the other protocols.
At a destination network, one or more routers may be utilized to receive incoming data packets and route the packets to other internal networks such as local area networks (LAN). The internal networks may further include servers that supply information to one or more clients. The servers are generally high-speed microcomputers, minicomputers or even mainframes. In some cases, the clients are internal to the network (i.e., at the back-end), and the router acts as a conduit for communication of data packets between the clients and the outside world. The back-end servers may provide various application functions for the clients, such as a database server that maintains the databases and processes requests from clients to extract data from or update the databases. In other cases, the clients are external to the network (i.e., at the front-end), and the router acts as a conduit for communication of data packets between the clients and the back-end servers. For example, an Internet application server at the back-end may host Web applications within the network that are accessed by clients outside the network. In still other cases, the clients are both internal and external to the network. The routers perform the functions of switching data packets between the internal and external networks, and balancing the load placed upon the back-end servers of the internal network by distributing message packets between the back-end servers in the most efficient and expeditious manner.
In view of the high volume of message traffic that they process and the relatively limited kinds of tasks that they perform, routers typically comprise dedicated switching processors having an architecture optimized to provide these functions. These conventional dedicated switching processors include a control module and a switching module that are viewed by the external networks as a single network entity. A drawback of such dedicated switching processors is that they can be very expensive due in part because they are manufactured in relatively low volumes as compared with other general-purpose computer systems. Moreover, the software that provides the message routing and load balancing functions must be written specifically for the dedicated switching processors, which further increases the cost of purchasing, operating and maintaining such systems. An additional drawback of dedicated switching processors is that most modifications to their functionality require a hardware change, which is typically more expensive and difficult than a software change.
A further disadvantage of dedicated switching processors is that it is cumbersome to communicate data packets between the switching module and the control module. Generally, the control module communicates with the switching module through special internal interfaces that add overhead to both the control module and the switching module, and is thus undesirable. For example, the control module may include network applications that operate at the user level, and data input and output for the network applications is handled at the operating system level. The operating system communicates with the network devices and issues interrupts to the network applications at the user level to indicate the receipt of data. These conventional systems are inefficient since processing of the network applications is stopped each time an interrupt is issued, and the involvement of the operating system further reduces the efficiency of the network applications.
It would therefore be very desirable to provide the message routing and load balancing functions of a network router within a general-purpose symmetrical multiprocessor (SMP) computer system. Such general-purpose multiprocessor computer systems are less expensive than conventional systems due to their larger volume production, and changes to their functionality can be readily accomplished by modifying their software rather than their hardware. It would additionally be desirable to provide network applications operating on a general-purpose multiprocessor computer system direct access to the network interfaces and to run the network applications on a dedicated processor which is not interrupted. Certain applications such as Internet telephony or fax applications would particularly benefit from such direct network access.
In accordance with the teachings of the present invention, a data packet switching and server load balancing device is provided by a general-purpose multiprocessor computer system. The general-purpose multiprocessor computer system comprises a plurality of symmetrical processors coupled together by a common data bus, a main memory shared by the processors, and a plurality of network interfaces each adapted to be coupled to respective external networks for receiving and sending data packets via a particular communication protocol, such as Transmission Control Protocol/Internet Protocol (TCP/IP) or User Datagram Protocol (UDP).
More particularly, a first one of the processors is adapted to serve as a control processor and remaining ones of the processors are adapted to serve as data packet switching processors. The data packet switching processors are each coupled to at least one of the plurality of network interfaces. The control processor receives raw load status data from agents running on the back-end application servers and generates load distribution configuration data therefrom. The load distribution configuration data is stored in the main memory for access by the data packet switching processors. The switching processors route received ones of the data packets to a selected one of the external networks in accordance with information included in a header portion of the data packets and the load distribution configuration data. The switching processors perform periodic polling of corresponding ones of the network interfaces to detect a received one of the data packets therein. In addition, the switching processors re-write the routing information included in the header portion of the data packets to reflect the selected one of the external networks.
In an embodiment of the invention, a multiprocessor computer system comprises a plurality of network interfaces each adapted to be coupled to respective external networks for receiving and sending data packets to and from remote devices coupled to the external networks via a particular communication protocol. The multiprocessor computer system further comprises a plurality of symmetrical processors including a control processor and at least one switching processor. The switching processor further includes at least one network application executing thereon. The control processor further includes an operating system portion having a kernel memory and at least one network driver communicating with the plurality of network interfaces. A buffer descriptor list is accessible by the network application and the network driver. The buffer descriptor list defines the status of buffers provided in the kernel memory that are used for temporary storage of data packets transferred between the network application and the plurality of network interfaces via the network driver. Data packets received by the network interfaces from the external networks directed to the network application are placed in selected ones of the buffers by the network driver for direct access by the network application. Similarly, data packets transmitted from the network application to the external networks are placed in other selected ones of the buffers for direct access by the network driver.
A more complete understanding of the software interface between switching and control modules of a computer data packet switching and load balancing system will be afforded to those skilled in the art, as well as a realization of additional advantages and objects thereof, by a consideration of the following detailed description of the preferred embodiment. Reference will be made to the appended sheets of drawings, which will first be described briefly.